Aircraft on-board oxygen generating systems (OBOGS) have been developed for producing oxygen-enriched air that serves as breathing gas for one or more aircraft occupants (e.g., a pilot). The OBOGS includes an oxygen concentrator, which contains one or more particle beds commonly referred to as sieves. The sieves contain an adsorbent (e.g., zeolite) having a high affinity for nitrogen. As the OBOGS directs airflow through the oxygen concentrator, the sieves remove nitrogen from the air and the air's oxygen content is consequently increased. The resulting oxygen-enriched air is then routed to, for example, an oxygen breathing mask of the type worn by the pilot of a jet.
The air supplied to the OBOGS may be warm and moist. As this warm, moist air cools, condensation forms within the ducting of the OBOGS. Over time, this condensation may pools and wet the sieves. Wetting of the sieves may significantly degrade their performance. In addition, wetting may decrease the sieves' operational lifespan and, thus, require premature OBOGS unit replacement. It is thus desirable to prevent the wetting of the sieves by minimizing the formation or preventing the collection of condensation within the OBOGS.
Certain devices have been developed that may minimize the formation of condensation within the ducting of the OBOGS. For example, a cyclonic separation device may be employed that rotates the pressurized air flowing through the OBOGS at a high rate of speed. This causes the moisture droplets carried by the air to spiral into a tubular cyclone filter, which then removes the moisture from the OBOGS. While cyclonic separation devices of this type are fairly reliable at reducing air moisture content, the cyclone filter permits a substantial loss of pressurized air (“air leakage”) during operation of the OBOGS, which negatively impacts the efficiency of the OBOGS system.
As an alternative to a cyclone separation device, a mixing valve may instead be employed within the OBOGS to minimize the formation of condensation. The mixing valve introduces hot, dry air from an upstream source into the warm, moist air entering the OBOGS. The hot, dry air mixes with the warm, moist air thereby reducing the moisture content thereof, consequently decreasing the formation of condensation within OBOGS ducting. Although such a mixing valve may effectively reduce the volume of collected condensation over a given period of time, the inclusion of such a mixing valve adds considerable weight and cost to the OBOGS system.
It should thus be appreciated that it would be desirable to provide an on-board oxygen generating system configured to minimize retained condensation. In particular, it would be desirable to provide a drain valve assembly that may be employed within an OBOGS that permits condensation to drain therefrom. Furthermore, it would be advantageous for such a drain valve assembly to automatically close when the OBOGS is activated so as to minimize the loss of pressurized air. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.